Semifluorinated alkanes are physically, chemically and physiologically inert compounds, which find application in medicine, in particular in the ophthalmic and dermatological field.
As described in Chem. Rev. 2009, 109, 1714-1792, a process commonly used for the production of semifluorinated alkanes is a process comprising the free radical addition of F-alkyl iodides, CnF2n+1I, to a multiple bond, followed by reductive dehalogenation of the resulting iodinated adduct. The addition of CnF2n+1I onto a terminal alkene is commonly conducted in the presence of an azonitrile type radical generating chain initiator (e.g. 2,2′-azobis(isobutyronitrile), AIBN) according to the following scheme:

Reductive dehalogenation of the iodo-diblock intermediate CnF2n+1CH2CHICm−2H2m−3 is commonly performed with zinc powder and gaseous HCl in ethanol or another alcohol, acetic acid or aqueous HCl. In alternative processes, tributyltin hydride and LiAlH4/ether are also used. Unsaturated diblocks can be converted to saturated ones using standard catalytic (rhodium or palladium on charcoal) hydrogenation procedures under pressure. Thorough purification of the diblock compounds is indispensable, especially when physicochemical investigation or biomedical applications are intended. It is usually achieved by distillation or recrystallization, sometimes followed by sublimation or passage over an alumina column. Filtration over activated alumina is strongly recommended when elimination of traces of potentially toxic material is essential.
Similar to the linear semifluorinated alkanes, the synthesis of semifluorinated alkanes with branched hydrocarbon chains comprises the free radical addition of F-alkyl iodides CnF2n+1 to a multiple bond, followed by reductive dehalogenation of the resulting iodinated adduct. An example of reductive dehalogenation of a iodinated compound with branched hydrocarbon chain has been reported as follows:

EP 0877 010 B1 describes inter alia the synthesis of 1-perfluorbutyl-3-methyl-butane in which reductive dehalogenation is performed with Zn/HCl.
The process comprising reductive dehalogenation by using Zn/HCl results in low yield and low purity, due to the presence of unsaturated species in the final product.
As another process for the production of semifluorinated alkanes, a process comprising reductive dehalogenation of the iodinated adduct by using Pd/C and H2 has been reported, see WO 97/12852. This process however requires the use of pressure reactors, long reaction time and results not to be economical.